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High-intensity focused ultrasound beam path visualization using ultrasound imaging
송재희,장진호,유양모 한국음향학회 2020 韓國音響學會誌 Vol.39 No.1
In High-Intensity Focused Ultrasound (HIFU) treatment, effective localization of HIFU focus is important for developing a safe treatment plan. While Magnetic Resonance Imaging guided HIFU (MRIgHIFU) can visualize the ultrasound path during the treatment for localizing HIFU focus, it is challenging in ultrasound imaging guided HIFU (USIgHIFU). In the present study, a real-time ultrasound beam visualization technique capable of localizing HIFU focus is presented for USIgHIFU. In the proposed method, a short pulse, with the same center frequency of an imaging ultrasound transducer below the regulated acoustic intensity (i.e., Ispta < 720 mW/cm2), was transmitted through a HIFU transducer whereupon backscattered signals were received by the imaging transducer. To visualize the HIFU beam path, the backscattered signals underwent dynamic receive focusing and subsequent echo processing. From in vitro experiments with bovine serum albumin gel phantoms, the HIFU beam path was clearly depicted with low acoustic intensity (i.e., Ispta of 94.8 mW/cm2) and the HIFU focus was successfully localized before any damages were produced. This result indicates that the proposed ultrasound beam path visualization method can be used for localizing the HIFU focus in real time while minimizing unwanted tissue damage in USIgHIFU treatment.
Speckle Reduction Techniques in Medical Ultrasound Imaging
Jihoon Park,강진범,장진호,유양모 대한의용생체공학회 2014 Biomedical Engineering Letters (BMEL) Vol.4 No.1
Effective speckle reduction is important for enhancing imagequality and improving our understanding of medical ultrasoundimaging. Various speckle reduction techniques, such asfrequency compounding (SR-FC), spatial compounding (SRSC),and post filtering (SR-PF), have been proposed. In SRFC,uncorrelated sub-images, which are obtained by eithervarying the center frequency on transmission or by dividingthe spectrum of radio-frequency (RF) signals on reception,are compounded to lower speckle. In SR-SC, the sub-imagesare acquired at different beam orientations at the expense oftemporal resolution. On the other hand, in SR-PF, instead ofcompounding multiple sub-images, a specially designed spatialfilter, e.g., Laplacian pyramid-based nonlinear diffusion, isapplied to a single image. These techniques can be integratedtogether to maximize the effects of speckle reduction. Thisreview briefly introduces the principles behind three specklereduction techniques and describes their own strengthsand weaknesses. Finally, some clinical examples of specklereduction techniques are presented.